Currently, the deployment of HSDPA technologies in Time-Division Synchronization Code Division Multiple Access (TD-SCDMA) and Wideband Code Division Multiple Access (WCDMA) systems has provided a higher data rate, a shorter service response time and improved service reliability.
A transmission channel introduced in the TD-SCDMA and WCDMA HSDPAs is a High Speed Downlink Shared Channel (HS-DSCH), which is used as a bearer of higher layer data from a User Equipment (UE) and corresponds to a physical channel of High Speed Physical Downlink Shared Channel (HS-PDSCH).
The Adaptive Modulation and Coding (AMC) technology deployed in the HSDPA is mainly applied to the HS-DSCH, so that a UE in an advantageous position may be provided with a higher data rate with the combination of the AMC and the Hybrid Automatic Repeat reQuest (HARQ), thereby improving an average throughput of a cell.
Furthermore, with the AMC modulation scheme without changing the transmission power, the transmission power of a Base Station is sufficiently utilized. When a channel for a UE is of a relatively high quality, higher order modulation and a higher coding rate are used at a network side and the UE is assigned with a higher data rate; and when the channel for the UE is degraded, lower order modulation and a lower coding rate are used at the network side and the UE is assigned with a lower data rate.
However, no power control is performed in the HS-DSCH of the prior art. When the transmission power of the Base Station is excessively high and exceeds a dynamic range of a receiver in the UE, the receiver in the UE may be saturated, so that the receiving performance is degraded. Furthermore, when the channel for the UE has a high quality and the transmission in the HS-DSCH is at the predetermined power, the Signal-to-Noise Ratio (SNR) may be higher than that required for the highest transmission rate of the UE, thus, system interference is increased, throughput of the cell is decreased and the power is wasted.